Loud fan and temperature gauge goes up

Tiny
MISSCAT
  • MEMBER
  • 2003 HYUNDAI ELANTRA
  • 2.0L
  • 4 CYL
  • FWD
  • MANUAL
  • 150,000 MILES
The fan is really loud and the temperature gauge goes up past the half way mark, almost to the red line while driving or idling. When I turn on the heat, it goes back to normal. No visible leaks. Both fans are working, no broken blades.
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Thursday, February 13th, 2014 AT 9:13 PM

9 Replies

Tiny
CARADIODOC
  • EXPERT
The first suspect should be the radiator. Run your fingertips over the cooling fins. If they crumble like a rotten chocolate chip cookie, they aren't able to give up the heat to the air. The clue is the heater core, which is a small radiator, is doing the cooling when you turn the heater on.
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Thursday, February 13th, 2014 AT 11:16 PM
Tiny
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Cooling fins are fine
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Friday, February 14th, 2014 AT 12:04 AM
Tiny
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Thank you for the reply by the way!
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Friday, February 14th, 2014 AT 12:05 AM
Tiny
CARADIODOC
  • EXPERT
Feel the upper radiator hose when the engine is running hotter than normal. It should be too hot to hold onto for very long. If it is just warm, there is not enough circulation through the radiator and it may be partially plugged. You may be able to feel cool and hot areas across the radiator. If both the upper and lower hoses are really hot, the radiator is not giving up its heat. That has to be due to a serious butterfly collection in the fins or the fins are corroded. Or something is blocking the air flow like a piece of cardboard that someone put in there.
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Friday, February 14th, 2014 AT 12:45 AM
Tiny
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  • MEMBER
Okay, thank you. I will try this when I am off work in a couple of hours. I also forgot to mention, upon researching and it jogging my memory A while back it started happening where when I am idling and have the heat going, it doesn't blow out hot air until I start accelerating. I haven't noticed if it still does it. I assume it does and it didn't just go away somehow. I'm not sure if that makes a difference to you or not.
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Friday, February 14th, 2014 AT 1:06 AM
Tiny
CARADIODOC
  • EXPERT
No hot air until accelerating is typical of low coolant level but it can also be caused by a leaking cylinder head gasket. A leaking head gasket can also cause overheating because if combustion gases sneak into the cooling system it can pool under the thermostat and make it not open. Thermostats have to be hit with hot liquid to open. Hot air wont do it. When the thermostat stays closed, it blocks coolant flow to the radiator.

Your mechanic can do a chemical test at the radiator to check for a leaking head gasket. That involves drawing air from it while the engine is running, through a glass cylinder partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.
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Friday, February 14th, 2014 AT 2:14 AM
Tiny
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Like think I found the problem? The top hose is hot with no cold spots and the lower hose is cold. They are both supposed to be hot, correct?
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Friday, February 14th, 2014 AT 3:07 AM
Tiny
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Or is it just the top that's supposed to be hot.
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Friday, February 14th, 2014 AT 3:08 AM
Tiny
CARADIODOC
  • EXPERT
The lower hose is supposed to be much cooler indicating the heat was given up by the radiator. Be sure the coolant is full. Check the level in the radiator and the reservoir after the engine has cooled down.
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Friday, February 14th, 2014 AT 1:48 PM

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